add a vignette that illustrates the use of rJavaEnv with any Java/rJava-dependent R package

[e-kotov]

Please choose any rJava-dependent R package (you can choose from the ones listed in reverse depends or reverse imports here).

You may also choose a package that does not depend on {rJava} directly but relies on java executable to be installed and available as a command line tool. Examples of such packages are:

• {opentripplanner}
• {RSelenium}
• {photon}

Create a basic vignette that illustrates how to setup the correct Java version for your selected package.